In the treatment of cerebrovascular disorders such as intracranial aneurysms and arteriovenous malformations (AVMs), there are two options for treatment: a craniotomy or minimally-invasive surgery (MIS) using micro-catheters. In the case of an aneurysm, endovascular occlusion using detachable coils, deployed via a micro-catheter, has become the preferred method over clip ligation through craniotomy. This is due to the lower rates of inpatient mortality, shorter hospital stays and lower treatment costs associated with the less invasive method.
The effectiveness of this method, however, is limited by the inability of current micro-catheters to reach and adequately treat aneurysms. Studies on the deployment of Guglielmi detachable coils (GDC), for example, revealed that 38 per cent of failures are the direct result of the inability to catheterise the aneurysm.
Catheters with variable distal ends are becoming increasingly popular, and are available in a myriad of configurations including mechanical tension-wire, electrically controlled memory-shape alloy and remote magnetic field navigation. All of these catheters, however, are limited to regions of the vasculature significantly greater than 1 mm in scale. This is due to their complexity of construction and their inability to navigate tight radius bends, which are synonymous with the neurovascular system. GDC procedures demand the ability to access regions of the vasculature as low as 350 μm in diameter.
In the first step of such catheter-based endovascular neurosurgery, a guidewire is inserted to just beyond the injured location. To reach the location, the guidewire must be pushed past the tortuous passage in the carotid artery at the base of the skull, and several Y-junctures must be navigated to reach even the most proximal locations within the brain. Indeed, roughly 85% of the brain cannot be reached with current technology. Guidewires are simply pushed back and forth repeatedly by the surgeon while viewed via x-ray to hopefully pass into the desired location. No rotation of the guidewire is possible, and only a few Y-junctions may be passed with the guidewire before too much friction risks rupture of the arteries near these junctures. Once the guidewire is correctly positioned, a micro-catheter is introduced over the guidewire to the injured location.